The effects of mutations in nolL and nodZ genes of Bradyrhizobium sp WM9 (Lupinus) upon root nodule ultrastructure in Lupinus luteus L.

In Lupinus luteus L. - Bradyrhizobium sp. WM9 (Lupinus) symbiosis, mutation s in nolL and nodZ genes (no fucose or no acetyl group at the fucose) did n ot hinder nodule morphogenesis significantly. The effects of both mutations , as observed in nodule anatomy and ultrastructure, were the same. The muta tions affected the early stage of symbiosome population formation and thus the differentiation of bacteroid tissue. In mutant-inoculated plants, the b acteroid tissue developed more cell-wall-associated bacterial enclaves. Als o, the disappearance of vesicles accumulating cell-wall-like material was d elayed. The symptoms of mutations were transient and the plants recovered f rom the initial nitrogen starvation.